21608018 has 4 divisors (see below), whose sum is σ = 32412030. Its totient is φ = 10804008.

The previous prime is 21607991. The next prime is 21608029. The reversal of 21608018 is 81080612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 15737089 + 5870929 = 3967^2 + 2423^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5402003 + ... + 5402006.

Almost surely, 2^21608018 is an apocalyptic number.

21608018 is a deficient number, since it is larger than the sum of its proper divisors (10804012).

21608018 is a wasteful number, since it uses less digits than its factorization.

21608018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10804011.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 21608018 is about 4648.4425348712. The cubic root of 21608018 is about 278.5297852531.

The spelling of 21608018 in words is "twenty-one million, six hundred eight thousand, eighteen".